"This is a tragedy that should not have happened, a memorial service that should not be taking place, and victims that should not be victims," Wayne LaPierre, NRA executive vice president, said on NBC's "Meet the Press" program.

"In a post 9/11 world, a naval base within miles from Congress, the White House ... largely left unprotected," he said.

Law enforcement authorities have identified the Navy Yard shooter as Aaron Alexis, 34, whose primary weapon in Monday's rampage was a shotgun that he had recently purchased.

The Department of Veterans Affairs has said Alexis was treated for insomnia, while Rhode Island police had warned the Navy in August that Alexis reported "hearing voices" and believed people were following him and "sending vibrations into his body."

The NRA is calling for layers of security established around military bases where personnel who are trained in firearms are largely disarmed on the base, LaPierre said.

"There weren't enough good guys with guns. When the good guys with guns got there, it stopped," he said.

LaPierre said the mental health situation in the country is in "complete breakdown" and public outrage should be directed toward that as well as the criminal justice system that releases dangerous offenders onto the streets.

"Let's fix this broken system right now which nobody wants to fix," LaPierre said. "If we leave these homicidal maniacs on the street, they don't obey the law, they could care less about it, they are going to kill."